Proton pump inhibitors represented by omeprazole, which suppress secretion of gastric acid for the treatment of peptic ulcer, reflux esophagitis and the like, have been widely used in clinical situations. However, the existing proton pump inhibitors are associated with problems in terms of effect and side effects. To be specific, since the existing proton pump inhibitors are unstable under acidic conditions, they are often formulated as enteric preparations, in which case several hours are required before onset of the effect, and about 5 days to exhibit maximum efficacy by consecutive administration. In addition, since the existing proton pump inhibitors show variation of treatment effects due to metabolic enzyme polymorphism and drug interaction with medicaments such as diazepam and the like, an improvement has been desired.
As compounds having a proton pump inhibitory action, patent document 1 describes a compound represented by the formula:
whereinring A is a saturated or unsaturated 5- or 6-membered ring group optionally containing, as a ring-constituting atom besides carbon atoms, 1 to 4 heteroatoms selected from a nitrogen atom, an oxygen atom and a sulfur atom, and the ring-constituting atoms X1 and X2 are each a carbon atom or a nitrogen atom, R1 is an optionally substituted aryl group or an optionally substituted heteroaryl group, R2 is an optionally substituted alkyl group, an optionally substituted aryl group or an optionally substituted heteroaryl group, andR3 is a substituent on the ring-constituting atom other than X1, X2 and X3, which optionally has substituent(s) selected from a lower alkyl group, a halogen atom, a cyano group and oxo.